SCH 3U/4C - Grade 9 & 10 Science Review - Matter, Properties & Changes

Matter – anything that has mass & volume.

 

Changes of State – melting, freezing, evaporation, condensation, sublimation, deposition

Classification of Matter

Physical Property – a property that can be determined without altering the chemical composition of the material (ex. colour, odour, melting point)

Quantitative Property – a measurable property that has a number and a unit (ex. density, mass)

Qualitative Property – simply a description that does not have a measurement (ex. colour, odour)

Chemical Property – a property that describes how matter behaves in the presence of other substances or when subjected to heat, light or electricity (ex. iron reacts with oxygen to form rust)

Physical Change – a change in which the chemical identity or composition of the sample of matter remains the same (ex. cutting wood, all changes of state, dissolution)

Chemical Change – a change in which at least one new substance is formed (ex. burning wood)

Homework

Answer Keys:

 

SCH 3U/4C - Chemical Reaction Review

Review:

Answers:

Success Criteria:

• nomenclature (name ↔ formula)
• be able to write out word, skeleton and balanced equations
• be able to provide appropriate state symbols when requested
  
• be familiar with the types of chemical reactions - types (S, D, SR, DR, combustion, exothermic, endothermic, oxidation, neutralization, etc)
  
• be able to predict products for any types of S, D, SR, DR and combustion reactions
• be able to use the Activity Series with SR reactions
• be able to use the Solubility Rules with DR reactions
  
• be able to write total ionic and net ionic equations for DR reactions
• be familiar with the "Reactions in Industry" reading assignment (do NOT memorize reaction equations)
  

SCH 4U - Chemical Kinetics

Chemical kinetics is the study of the rate at which reactions occur and how to speed up or slow down the reaction. 

If we compare power generated by the combustion reaction of carbon with power generated by the decomposition of nitroglycerin, it will become obvious why the rates of reactions are important:

C(s) + O₂(g) → CO₂(g), slow reaction with ΔH = -394 kJ

P = E/t = 394 kJ/large = small power (not scary)

 

C₃H₅(NO₂)₃(l) → 3CO₂(g) + ½NO₂(g) + 5/2H₂O(g) + 5/2N₂(g), fast reaction with ΔH = -190 kJ

P = E/t = 190 kJ/small = large power (very, very scary)

 

Average Rate & Instantaneous Rate

Reaction rate is the change in the concentration of a reactant or a product per unit time (rate = Δ[R]/Δt or rate = Δ[P]/Δt).

• Reaction rate has units which can be written as mol/L/s or M/s or molL^-1s^-1or Ms^-1.
  

Average reaction rate can be calculated over a given time interval.

This can be determined in two ways - using a concentration versus time graph, determine the slope of a line joining two points on the curve (a sectant line) or calculate as below.

The graph to the left represents the change in reactant concentration over time. The graph to the right represents the change in product concentration over time. 

ex.  What is the rate of consumption of each reactant when the rate of production of ammonia is 4.0 x 10^-3 Ms^-1?     N₂(g)  +  3H₂(g)  →  2NH₃(g)

👉 set up a "rate ratio" which is similar to a mole ratio - use the coefficients in front of each substance to create the ratio

 - rate(N₂)÷1 = rate(NH₃)÷2

👉 plug in the known value, given in the question and solve for the unknown value

  rate(N₂) = -4.0 x 10^-3 Ms^-1÷2

  rate(N₂) = - 2.0 x 10^-3 Ms^-1  

∴ the rate of consumption of nitrogen gas is 2.0 x 10^-3 Ms^-1

Note:  We have to make one side of the equation negative because consumption and production are not the same (they are opposite of each other).  Thus, we would not be able to use the equal sign.  By making consumption = -production, we can circumvent this issue).

 

- 1/3 rate(H₂) = ½ rate(NH₃)

        rate(H₂) = - 3/2 (4.0 x 10^-3 Ms^-1)

        rate(H₂) = - 6.0 x 10^-3 Ms^-1  

∴ the rate of consumption of hydrogen gas is 6.0 x 10^-3 Ms^-1

 

Instantaneous reaction rate is calculated for an instant in time - determine the slope of a tangent line at the point on the curve for the instant in time.

 

 

Measuring Reaction Rates

Reactions that Produce a Gas

• for a reaction that produces a gas, such as the reaction of zinc with hydrochloric acid

• the experimenter can collect and measure the volume and/or pressure of the produced gas to follow the rate of the reaction

 

Reactions that Involve Ions

• for a reaction that produces ions

• the experimenter can measure the conductivity of a solution to follow the rate of the reaction

 

Reactions that Change Colour

• for a reaction in which a coloured reactant disappears or a coloured product is produced

• the experimenter can measure colour intensity using a spectrophotometer

 

Homework #1-6

Homework and Answer Keys can be found here.

SCH 3U - Reactions in Industry

Would you like an opportunity to do a reading assignment?

An assignment that will boost your mark and make you a more intelligent, well-rounded individual?

Of course you would...and just to provide an extra incentive, I have already put the marks into Edsby for you.

So, what do I have to do to keep the marks, you may ask?

Read the 'Reactions in Industry' section in the textbook and fill in the chart below.  You have 'til the day of the test at the start of class.  No later or you will be out of luck.

 

SCH 3U/4C - Predicting Products for Double Replacement Reactions

Predicting Products – Double Replacement Reactions  

Remember that double replacement reactions involve the swapping of the cations between the two reactants to produce two new product compounds.

Use the valences of the elements to create the formulae of the substances.  The valence that an element or polyatomic ion starts with as a reactant will continue to be its valence even when combined into the new product (for instance, iron uses its +3 valence as a reactant and as a product).

    iron (III) nitrate + sodium hydroxide → iron (III) hydroxide + sodium nitrate

Fe(NO₃)₃ + 3NaOH → Fe(OH)₃ + 3NaNO₃

Notice that a precipitate forms, but what combination of ions caused this?

 

Using Solubility Rules 

So, how does one determine if an ionic compound is soluble in water, you might ask.  By, using the solubility rules, of course.

Keep in mind:

When the rule tells you that the compound is "soluble" you will indicate this with the state symbol (aq).

When the rule tells you that the compound has "low solubility" that means it is not soluble to any appreciable amount and would precipitate out of solution.  So, you indicate this with the state symbol (s).

Let's try some examples:

Using the Solubility Rules

 

So, let's go back to the example from the beginning of the lesson.  Using the rules, we find that iron (III) hydroxide is insoluble and sodium nitrate is soluble.  We use (s) to represent a precipitate or solid and (aq) to represent the compound which remains in solution, which is said to be aqueous. 

Fe(NO₃)₃(aq) + 3NaOH(aq) → Fe(OH)₃(s) + 3NaNO₃(aq)

 

Total & Net Ionic Equations

A total ionic equation is a chemical reaction equation that shows the separation of soluble ionic compounds into their ions.

A net ionic equation is a chemical reaction equation that shows only reacting particles.

Spectator ions are those ions which appear on both sides of the equation and are crossed out.

 

TryIt!  Finish the word equation below and create a balanced equation.  Using the solubility rules, indicate whether the products are soluble or not.  Also, write out the total ionic and net ionic equations.

iron (III) nitrate + sodium hydroxide →

The answer, and an accompanying video, can be found below  

TryIt! Part 2  Finish the word equation below and create a balanced equation.  Using the solubility rules, indicate whether the products are soluble or not.  Also, write out the total ionic and net ionic equations.

silver nitrate + magnesium chloride →

The answer can be found below.

 

Special Double Replacement Reactions

Reactions that Produce Gas

Some reactions are not straight forward.  For instance the mixing of acid and washing soda results in a two step reaction, since the carbonic acid produced (through a double replacement reaction) in the first step decomposes in the second step:

2HCl(aq)  +  Na₂CO₃(aq)  →  2NaCl(aq)  +  H₂CO₃(aq)

H₂CO₃(aq)  →  H₂O(l)  +  CO₂(g)

___________________________________________________

2HCl(aq)  +  Na₂CO₃(aq)  →  2NaCl(aq)  + H₂O(l)  +  CO₂(g)

Notice that the equations in the two steps, when added together, allow for the crossing out of carbonic acid.  The equation below the line shows the overall reaction.

Neutralization Reaction

Mixing an acid and a base results in the production of a salt and water.

Acid  +  Base  →  a Salt  +  Water

HCl(aq)  +  NaOH(aq)  →  NaCl(aq)  + H₂O(l) 

 

TryIt! Answer:

iron (III) nitrate + sodium hydroxide → iron (III) hydroxide + sodium nitrate

Fe(NO₃)₃(aq) + 3NaOH(aq) → Fe(OH)₃(s) + 3NaNO₃(aq)

Fe³⁺(aq) + 3NO₃^-(aq) + 3Na⁺(aq) + 3OH^-(aq) → Fe(OH)₃(s) + 3Na⁺(aq) + 3NO₃^-(aq)

Fe³⁺(aq) + 3OH^-(aq) → Fe(OH)₃(s) 

Check out this video, if you want to see me arrive at the answer above.  When I recorded the video, I had my phone turned sideways, so try not to get a neck crick - sorry.

TryIt! Part 2 Answer:

Homework:

Answers: